I'm no macro expert, but in my limited experience, the longer focal lengths are preferable. This is certainly true when dealing with subjects that might move or fly away if you get too close.
Since it is a macro lens, I would not worry too much about auto focus capabilities -- you should be on a tripod and manually focusing. That being said, a great budget lens would be a used Tamron 90mm f/2.8 macro. It won't auto-focus with your camera, but again... From what I read about it a few years ago when I was looking at macro lenses, it holds its own with the Nikkor 105mm macro, and some people say it is sharper. There may be a newer version that has a built-in motor that would auto focus with your camera, making it useable for non-macro applications.
By the way, when I used my tamron, I wished I had more focal length, but I think it would have cost me quite a bit more money given what was out there. Most people think that the old nikkor 200mm AF macro lens is a great one, and the (may be getting this wrong) sigma 150mm macro is also a lens that gets great reviews. If the sigma is HSM (I think it is?), it would auto focus, so it would be a good general telephoto lens as well.
By the way, all of these lenses are great portrait lenses.